Device having a pulsation reducing structure, a passage forming body and compressor

ABSTRACT

Pulsation of gas spreads from a pulsation source to a gas passage in a device. A muffler is located in a part of the gas passage. A combined passage is located upstream or downstream of the muffler with respect to a flowing direction of gas. The combined passage includes a restricting passage and a pressure restoring passage, which are connected in series. The pressure restoring passage is located downstream of the restricting passage with respect to the flowing direction of gas. The muffler is located between the pulsation source and the combined passage in the gas passage. Therefore, the device obtains sufficient pulsation reducing effect and suppresses pressure loss.

BACKGROUND OF THE INVENTION

The present invention relates to a device having a pulsation reducingstructure. The present invention also pertains to a passage forming bodyand a compressor.

In a scroll compressor disclosed in Japanese Laid-Open PatentPublication No. 2002-285981, an oil separator is located in a fronthousing member. An oil separating chamber, which forms part of the oilseparator, is connected to a discharge chamber defined at the back of afixed scroll. The oil separating chamber accommodates a cylindricalmember, which forms part of the oil separator. Refrigerant gas in thedischarge chamber is introduced into the oil separating chamber.Lubricant oil included in the refrigerant gas introduced into the oilseparating chamber is separated from the refrigerant gas.

The cylindrical member, which forms part of the oil separator, alsofunctions to reduce pulsation of discharged gas.

The inner diameter of the cylindrical member needs to be reduced toobtain sufficient pulsation reducing effect. However, if the innerdiameter of the cylindrical member is excessively reduced, a greatpressure loss is generated. Therefore, it is difficult to reduce theinner diameter of the cylindrical member to obtain sufficient pulsationreducing effect.

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide adevice having a pulsation reducing structure that obtains sufficientpulsation reducing effect and suppresses pressure loss in devices havinga gas passage. The present invention also pertains to a passage formingbody and a compressor.

To achieve the above-mentioned objective, the present invention providesa device having a pulsation reducing structure. The device includes agas passage, a pulsation source connected to the gas passage, a mufflerfor reducing the pulsation and a combined passage located in the gaspassage. Pulsation of gas spreads from the pulsation source to the gaspassage. The muffler is located in a part of the gas passage. Thecombined passage is located upstream or downstream of the muffler withrespect to a flowing direction of gas. The combined passage includes arestricting passage and a pressure restoring passage. The restrictingpassage and the pressure restoring passage are connected in series. Thepressure restoring passage is located downstream of the restrictingpassage with respect to the flowing direction of gas. The muffler islocated between the pulsation source and the combined passage in the gaspassage.

According to another aspect of the invention, a passage forming bodyhaving a plurality of combined passages is provided. The combinedpassages are arranged in parallel. Each combined passage includes arestricting passage and a pressure restoring passage. In each combinedpassage, the restricting passage is combined with the pressure restoringpassage in series.

In addition, present invention may be applicable to provide a scrollcompressor. The compressor includes a compression mechanism including amovable scroll and a fixed scroll, the scrolls defining a compressionchamber, a discharge chamber for receiving gas discharged from thecompression chamber, a discharge gas passage for guiding discharge gasfrom the discharge chamber to the outside of the compressor. Arestricting passage is located in the discharge gas passage. A pressurerestoring passage is located in the discharge gas passage. The pressurerestoring passage is connected to the restricting passage in series andlocated downstream of the restricting passage with respect to a flowingdirection of gas.

Other aspects and advantages of the invention will become apparent fromthe following description, taken in conjunction with the accompanyingdrawings, illustrating by way of example the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

FIG. 1(a) is a cross-sectional view illustrating a compressor accordingto a first embodiment of the present invention;

FIG. 1(b) is an enlarged partial cross-sectional view of FIG. 1(a);

FIG. 2(a) is a cross-sectional view illustrating a compressor accordingto a second embodiment of the present invention;

FIG. 2(b) is an enlarged partial cross-sectional view of FIG. 2(a);

FIG. 3 is an enlarged partial cross-sectional view illustrating a thirdembodiment of the present invention;

FIG. 4 is a partial cross-sectional view illustrating a fourthembodiment of the present invention;

FIG. 5(a) is a partial cross-sectional view illustrating a fifthembodiment of the present invention;

FIG. 5(b) is a side view illustrating a passage forming body 66 shown inFIG. 5(a); and

FIG. 5(c) is a cross-sectional view taken along line VC-VC in FIG. 5(b).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the drawings, like numerals are used for like elements throughout.

A first embodiment of the present invention will now be described withreference to FIGS. 1(a) and 1(b).

As shown in FIG. 1(a), a scroll compressor 10 includes a rear housingmember 12 and a front housing member 31. A shaft support member 13 and afixed scroll 11 are inserted in and fixed to the rear housing member 12.The front housing member 31 is secured to the rear housing member 12 andthe fixed scroll 11. The rear housing member 12 and the front housingmember 31 form a housing of a device, which is the scroll compressor 10.The rear housing member 12 and the shaft support member 13 rotatablysupport a rotary shaft 14 by means of radial bearings 15, 16.

The rotary shaft 14 extends through the shaft support member 13 andprojects toward the fixed scroll 11. An eccentric shaft 17 is formedintegrally with the end of the rotary shaft 14 that projects from theshaft support member 13. The axis of the eccentric shaft 17 located at aposition decentered from the axis of the rotary shaft 14. The eccentricshaft 17 supports a bush 18 to which a balance weight 19 is integrallyformed. The bush 18 supports a movable scroll 20 by means of a radialbearing 21 such that the movable scroll 20 faces the fixed scroll 11.The movable scroll 20 rotates relative to the fixed scroll 11. Theradial bearing 21 is accommodated in a cylindrical portion 221, whichprojects from the rear surface of a movable scroll base plate 22 of themovable scroll 20.

The fixed scroll 11 includes a fixed scroll base plate 23 and a fixedvolute portion 24. The movable scroll 20 includes the movable scrollbase plate 22 and a movable volute portion 25. The fixed scroll baseplate 23, the fixed volute portion 24, the movable scroll base plate 22,and the movable volute portion 25 define sealed spaces S0 and S1. Themovable scroll 20 orbits as the eccentric shaft 17 rotates. Centrifugalforce created by the orbital movement of the movable scroll 20 iscancelled by the balance weight 19.

Columnar anti-rotation pins 27 (three or more) are fixed to the movablescroll base plate 22. The shaft support member 13 has circularanti-rotation bores 131, the number of which is the same as theanti-rotation pins 27. The anti-rotation bores 131 are arranged in thecircumferential direction of the shaft support member 13. The end ofeach anti-rotation pin 27 is inserted in the corresponding anti-rotationbore 131.

A stator 29 is secured to the inner circumferential surface of the rearhousing member 12. A rotor 30 is secured to the rotary shaft 14. Whenelectricity is supplied to a stator coil 291 of the stator 29, the rotor30 and the rotary shaft 14 rotate integrally. The stator 29 and therotor 30 construct an electric motor.

The movable scroll 20 orbits as the eccentric shaft 17 rotatesintegrally with the rotary shaft 14. An inlet 26 is formed in acircumferential wall of the rear housing member 12 and a circumferentialwall 111 of the fixed scroll 11. As the movable scroll 20 orbits,refrigerant gas in an external refrigerant circuit, which is not shown,is introduced into a suction chamber 112 inside the circumferential wall111 through the inlet 26. The refrigerant gas introduced into thesuction chamber 112 flows into the sealed spaces S0, S1 between thefixed scroll base plate 23 and the movable scroll base plate 22 from theperiphery of the fixed scroll 11 and the movable scroll 20. Lubricantoil is included in a refrigeration circuit, which includes thecompressor 10, and flows with refrigerant gas.

As the movable scroll 20 orbits, the circumferential surface of eachanti-rotation pin 27 slides along the circumferential surface of thecorresponding anti-rotation bore 131. The movable scroll 20 is preventedfrom rotating while being permitted to orbit. As the movable scroll 20orbits, the sealed spaces S1, S0 move toward the center of the scrolls11, 20, while the volume of each sealed space S1, S0 decreasing.

A discharge chamber 32 is formed in the front housing member 31. Therefrigerant gas compressed by the decrease in the volume of the sealedspaces S1, S0 is discharged to the discharge chamber 32 through adischarge port 231, which is formed in the fixed scroll base plate 23,while flexing a discharge valve flap 33. A retainer 34 limits theopening degree of the discharge valve flap 33. A compression reactionforce in the sealed spaces S1, S0 that acts on the movable scroll 20 isreceived by the shaft support member 13.

An outlet 311 is formed in the circumferential wall of the front housingmember 31. A pipe 35 is fitted to the outlet 311. That is, the pipe 35is formed separately from the front housing member 31, which defines thedischarge chamber 32 and the outlet 311. As shown in FIG. 1(b), the pipe35 includes a fitting portion 351, a restrictor 38, and a diffuser 39.The restrictor 38, the diffuser 39, and the fitting portion 351 arearranged in series in this order along a flowing direction ofrefrigerant gas from the discharge chamber 32 to the outside of thecompressor 10 via the outlet 311. In other words, a restricting passage381 in the restrictor 38 and a pressure restoring passage 391 in thediffuser 39 are connected in series in this order from the dischargechamber 32 toward the outside of the compressor 10. The cross-sectionalarea of the pressure restoring passage 391 is greater than thecross-sectional area of the restricting passage 381.

The pipe 35 is fitted to the outlet 311 with the fitting portion 351.The inner diameter of the fitting portion 351 is greater than the innerdiameter of the diffuser 39 and the restrictor 38. The inner diameter ofthe restrictor 38 is constant. The inner diameter of the diffuser 39gradually increases from the end close to the restrictor 38 toward theend close to the fitting portion 351. That is, the pressure restoringpassage 391 is widened in the flowing direction of refrigerant gas. Thewidening angle θ1 (see FIG. 1(b)) of the pressure restoring passage 391of the diffuser 39 is less than or equal to 20 degrees.

When refrigerant gas is discharged into the discharge chamber 32 throughthe discharge port 231 while flexing the discharge valve flap 33, therefrigerant gas collides with the inner wall of the front housing member31, or the refrigerant gas changes the flowing direction and flowstoward the pipe 35. Therefore, the lubricant oil included in therefrigerant gas is separated from the refrigerant gas. The lubricant oilseparated from the refrigerant gas is stored at the bottom of thedischarge chamber 32. The bottom of the discharge chamber 32 isconnected to a back pressure chamber 37 located at the back of themovable scroll base plate 22 via a return passage 36. The lubricant oilstored at the bottom of the discharge chamber 32 is supplied to the backpressure chamber 37 through the return passage 36 and used to lubricatethe radial bearings 16 and 21. Refrigerant gas in the discharge chamber32 flows to the external refrigerant circuit through the pipe 35.

The pipe 35 is suspended in the outlet 311 such that the lower end ofthe pipe 35 is separate from the inner wall of the front housing member31 and projects in the discharge chamber 32. That is, part of the pipe35 is located inside the discharge chamber 32. This structureeffectively prevents lubricant oil adhered to the inner wall of thefront housing member 31 from entering the pipe 35 by the operation ofthe refrigerant gas. That is, the pipe 35 functions as an oil separator,which separates lubricant oil from refrigerant gas.

As shown in FIGS. 1(a) and 1(b), the discharge port 231 and thedischarge chamber 32 are part of a gas passage in the compressor 10. Thedischarge chamber 32 functions as a muffler that is part of the gaspassage. The restricting passage 381 in the restrictor 38 and thepressure restoring passage 391 in the diffuser 39 form a combinedpassage 40 located downstream of the muffler, which is the dischargechamber 32 in this embodiment, in respect to the gas passage. Thepressure restoring passage 391, which forms part of the combined passage40, is located downstream of the restricting passage 381. The fixedscroll 11, the movable scroll 20, and the sealed spaces S0, S1 form apulsation source. The pulsation of discharge gas spreads from thepulsation source to the external refrigerant circuit via the dischargechamber 32 and the combined passage 40. The discharge chamber 32(muffler) and the restricting passage 381 reduce the pulsation ofdischarge gas. The muffler, which is the discharge chamber 32 in thisembodiment, is located between the pulsation source and the combinedpassage 40 in respect to the gas passage.

The first embodiment has the following advantages.

(1-1) In the restricting passage 381, the pressure of refrigerant gas isreduced as the flow rate of refrigerant gas increases. On the otherhand, the pressure of refrigerant gas that has moved from therestricting passage 381 to the pressure restoring passage 391 increasesas the flow rate of refrigerant gas is reduced in the pressure restoringpassage 391. That is, the pressure restoring passage 391 restores thepressure of refrigerant gas that has passed through the restrictingpassage 381. The pressure of refrigerant gas can be reduced in therestricting passage 381 by an amount that can be restored in thepressure restoring passage 391. Therefore, the cross-sectional area ofthe restricting passage 381 can be reduced to increase the pulsationreducing effect of the discharge gas.

(1-2) The pipe 35, which is provided with the combined passage 40, isfitted to the outlet 311 of the front housing member 31. In this case,the pipe 35 may be press-fitted or adhered with an adhesion to theoutlet 311. The pipe 35 is fitted to a gas passage (the outlet 311 inthis embodiment) the diameter of which is greater than or equal to themaximum outer diameter of the diffuser 39 by adjusting the outerdiameter of the fitting portion 351 to the diameter of the gas passage.The pipe 35 is easily formed by, for example, press working. Therefore,the size and the shape of the pipe 35 to which the combined passage 40is formed can be selected in accordance with the shape of a pipe usedfor the gas passage (the outlet 311 in this embodiment). Thus, therestricting passage 381 and the pressure restoring passage 391 are alsoeasily formed. Therefore, the pipe 35 is a favorable place for formingthe combined passage 40.

(1-3) The pipe 35 functions also as the oil separator. Forming thecombined passage 40 in the pipe 35, which functions as the oilseparator, reduces the number of parts as compared to a case in which apipe dedicated for pulsation reduction is used. This contributes toreducing the cost. Since a space for the pipe dedicated for pulsationreduction is unnecessary, the size of the compressor 10 is preventedfrom being increased.

(1-4) In restoring the pressure in the pressure restoring passage 391,it is important that the flow of refrigerant gas through the pressurerestoring passage 391 does not separate from the inner surface of thediffuser 39. The structure of setting the widening angle θ1 of thepressure restoring passage 391 to be less than or equal to 20 degrees iseffective in preventing the refrigerant gas flow from separating fromthe inner surface.

(1-5) The compressor 10 that causes pulsation of discharge gas is adevice that includes the muffler, which is the discharge chamber 32 inthis embodiment, as part of a gas passage. The present invention issuitable for such compressor 10.

A pulsation reduction structure according to a second embodiment of thepresent invention will now be described with reference to FIGS. 2(a) and2(b).

As shown in FIG. 2(a), a cylinder block 41, a front housing member 42,and a rear housing member 43 form a housing of a device, which is apiston type variable displacement compressor 44 in the secondembodiment. The front housing member 42 and the cylinder block 41 definea control pressure chamber 421. The front housing member 42 and thecylinder block 41 rotatably support a rotary shaft 45.

A rotary support 46 is fixed to the rotary shaft 45, and a swash plate47 is supported on the rotary shaft 45. The swash plate 47 is permittedto incline with respect to and slide along the rotary shaft 45. Guideholes 461 are formed in the rotary support 46 and guide pins 48 areconnected to the swash plate 47. Each guide pin 48 is fitted to one ofthe guide holes 461 to form a hinge mechanism. The hinge mechanismpermits the swash plate 47 to tilt with respect to the axial directionof the rotary shaft 45 and rotate integrally with the rotary shaft 45.

When the center of the swash plate 47 moves toward the rotary support46, the inclination of the swash plate 47 increases. The rotary support46 determines the maximum inclination of the swash plate 47. The swashplate 47 shown by a solid line in FIG. 2(a) is in the maximuminclination state. When the center of the swash plate 47 moves towardthe cylinder block 41, the inclination of the swash plate 47 decreases.The swash plate 47 shown by a chain double-dashed line in FIG. 2(a) isin the minimum inclination state.

Cylinder bores 411 (only one is shown) extend through the cylinder block41. Each cylinder bore 411 accommodates a piston 49. The rotation of theswash plate 47 is converted to reciprocation of the pistons 49 by meansof shoes 50. Thus, each piston 49 reciprocates in the correspondingcylinder bore 411.

A suction chamber 431 and a discharge chamber 432 are defined in therear housing member 43. Suction ports 511 are formed in a valve plate 51and a valve flap plate 53. Discharge ports 512 are formed in the valveplate 51 and a valve flap plate 52. Suction valve flaps 521 are formedon the valve flap plate 52, and discharge valve flaps 531 are formed onthe valve flap plate 53. As each piston 49 moves from the top deadcenter to the bottom dead center (from the right side to the left sidein FIG. 2(a)), refrigerant gas in the suction chamber 431 is drawn intothe corresponding suction port 511 while flexing the suction valve flap521 to enter the associated cylinder bore 411. When each piston 49 movesfrom the bottom dead center to the top dead center (from the left sideto the right side in FIG. 2(a)), refrigerant in the correspondingcylinder bore 411 is discharged to the discharge chamber 432 via thecorresponding discharge port 512 while flexing the discharge valve flap531.

The discharge chamber 432 is connected to the control pressure chamber421 with a supply passage 54. The control pressure chamber 421 isconnected to the suction chamber 431 with a release passage 55.Refrigerant in the control pressure chamber 421 flows to the suctionchamber 431 through the release passage 55.

An electromagnetic control valve 56 is located in the supply passage 54.The control valve 56 is closed when de-excited and prevents refrigerantfrom passing through. In this state, refrigerant is not supplied fromthe discharge chamber 432 to the control pressure chamber 421 via thesupply passage 54. Refrigerant in the control pressure chamber 421 flowsto the suction chamber 431 through the release passage 55. Therefore,the pressure in the control pressure chamber 421 decreases. Therefore,the inclination angle of the swash plate 47 increases. The compressordisplacement increases, accordingly. The control valve 56 is open whenexcited and permits refrigerant through. In this state, refrigerant issupplied from the discharge chamber 432 to the control pressure chamber421 via the supply passage 54. Therefore, the pressure in the controlpressure chamber 421 increases. Accordingly, the inclination angle ofthe swash plate 47 decreases, which decreases the compressordisplacement.

A muffler 57 is formed on the circumferential surface of the cylinderblock 41 and the circumferential surface of the front housing member 42.The muffler 57 has a cylindrical portion 58. The cylindrical portion 58is formed integrally with the cylinder block 41. The muffler 57 isconnected to the discharge chamber 432 via a discharge passage 59. Themuffler 57 is connected to the control pressure chamber 421 via an oilpassage 60. A pipe 61 is accommodated in and fitted to the cylindricalportion 58.

As shown in FIG. 2(b), the pipe 61 includes a nozzle 62, a restrictor63, and a diffuser 64. The nozzle 62, the restrictor 63, and thediffuser 64 are arranged in series in this order along a direction fromthe muffler 57 toward the outside of the compressor 44 via the interiorof the cylindrical portion 58. In other words, an introduction passage621 in the nozzle 62, a restricting passage 631 in the restrictor 63,and a pressure restoring passage 641 in the diffuser 64 are connected inseries in this order from the muffler 57 toward the outside of thecompressor 44. The inner diameter of the nozzle 62 gradually decreasesfrom the end close to the muffler 57 toward the restrictor 63. A smalldiameter portion of the introduction passage 621 is connected to therestricting passage 631. That is, the introduction passage 621 istapered toward the restricting passage 631. In other words, assumingthat the introduction passage 621 is the inlet of the restrictingpassage 631, the inlet is widened in a direction opposite to the flowingdirection of refrigerant gas.

The inner diameter of the restrictor 63 is constant, and the innerdiameter of the diffuser 64 gradually increases from the end close tothe restrictor 63 toward the end close to the outside of the compressor44. The widening angle θ1 (see FIG. 2(b)) of the diffuser 64 is lessthan or equal to 20 degrees. The widening angle θ2 (see FIG. 2(b)) ofthe nozzle 62 is greater than the widening angle θ1 of the diffuser 64.The inner circumferential surface of the nozzle 62 is connected to theinner circumferential surface of the cylindrical portion 58 in a bentstate as shown by an acute angle α in FIG. 2(b). That is, there is nostep having a substantially right angle between the innercircumferential surface of the nozzle 62 and the inner circumferentialsurface of the cylindrical portion 58.

When refrigerant gas is discharged into the muffler 57 through thedischarge passage 59, the refrigerant gas collides with the inner wallof the muffler 57, or the refrigerant gas changes the flowing directionand flows toward the cylindrical portion 58. Therefore, the lubricantoil included in the refrigerant gas is separated from the refrigerantgas. The passage of refrigerant gas extending from the muffler 57 to thecylindrical portion 58 narrows in the cylindrical portion 58. Thisprevents lubricant oil from entering the cylindrical portion 58. Thatis, the cylindrical portion 58 functions as an oil separator, whichseparates lubricant oil from refrigerant gas. The lubricant oilseparated from the refrigerant gas is stored at the bottom of themuffler 57. Refrigerant gas in the muffler 57 flows to the externalrefrigerant circuit, which is not shown, through the pipe 61.

The discharge passage 59 and the muffler 57 are part of the gas passagein the variable displacement compressor 44. The restricting passage 631in the restrictor 63 and the pressure restoring passage 641 in thediffuser 64 form a combined passage 65 located downstream of the muffler57 in respect to the gas passage. The pressure restoring passage 641,which forms part of the combined passage 65, is located downstream ofthe restricting passage 631. The pipe 61 is located in the cylindricalportion 58 to permit refrigerant gas to flow through the combinedpassage 65.

The pistons 49 and the cylinder bores 411 construct a pulsation source.The pulsation of discharge gas spreads from the pulsation source to theexternal refrigerant circuit via the discharge chamber 432, thedischarge passage 59, the muffler 57, and the combined passage 65. Themuffler 57 and the restricting passage 631 reduce the pulsation ofdischarge gas. The muffler 57 is located between the pulsation sourceand the combined passage 65 in respect to the gas passage.

The second embodiment has the same advantages as the advantages (1-1),(1-4), and (1-5) of the first embodiment. The pipe 61 can be fitted tothe cylindrical portion 58 by setting the outer diameter of the pipe 61in accordance with the inner diameter of the cylindrical portion 58. Thesize and the shape of the pipe 61 to which the combined passage 65 isformed can be selected in accordance with the shape of the pipe used forthe gas passage (the cylindrical portion 58 in the second embodiment).Therefore, the pipe 61 is a favorable place for forming the combinedpassage 65.

In the second embodiment, the pipe 61 is accommodated in the cylindricalportion 58. Therefore, if there is a step having a substantially rightangle at the inlet of the pipe 61, the step generates a great passageresistance with respect to the refrigerant gas. The passage resistancecauses pressure loss. However, the inner circumferential surface of thenozzle 62 is connected to the inner circumferential surface of thecylindrical portion 58 at an acute angle α. Therefore, the passageresistance applied to the refrigerant gas that flows into the pipe 61 issmall.

FIG. 3 shows a third embodiment of the present invention. As shown inFIG. 3, a pipe 61A includes a pressure restoring passage 641A, which isformed by smoothly connecting the inner circumferential surface of adiffuser 64A to the inner circumferential surface of the restrictor 63.In this case, the widening angle θ3 of the pressure restoring passage641A, which forms part of a combined passage 65A, represents the angleat the maximum diameter portion of the pressure restoring passage 641A.The widening angle θ3 of the pressure restoring passage 641A is lessthan or equal to 20 degrees.

A fourth embodiment will now be described with reference to FIG. 4.

The combined passage 40, which includes the restricting passage 381 andthe pressure restoring passage 391, is directly formed in the fronthousing member 31.

The fourth embodiment has the same advantages as the advantages (1-1),(1-4), and (1-5) of the first embodiment.

A fifth embodiment will now be described with reference to FIGS. 5(a),5(b), and 5(c). As shown in FIG. 5(a), an inlet 28 is formed in thecircumferential wall of the rear housing member 12 and thecircumferential wall 111 of the fixed scroll 11. A columnar passageforming body 66 is fitted in the inlet 28. A plurality of Combinedpassages 67 are formed in the passage forming body 66 and are arrangedin parallel. As the movable scroll 20 orbits, refrigerant gas in theexternal refrigerant circuit, which is not shown, is introduced into thesuction chamber 112 via the combined passages 67. The suction chamber112 serves as a muffler, which forms part of the gas passage in thecompressor 10. The combined passages 67 are located upstream of thesuction chamber 112 in respect to the gas passage.

As shown in FIGS. 5(a), 5(b), and 5(c), each combined passage 67 has apressure restoring passage 671, a restricting passage 672, and anintroduction passage 673. The pressure restoring passage 671 is locateddownstream of the restricting passage 672. The restricting passage 672is located downstream of the introduction passage 673. The diameter ofthe introduction passage 673 gradually decreases from the end close tothe external refrigerant circuit (outside of the compressor 10) towardthe restricting passage 672. A small diameter portion of theintroduction passage 673 is connected to the restricting passage 672. Asdescribed above, the pulsation source is formed by the fixed scroll 11,the movable scroll 20, and the sealed spaces S0, S1. The pulsation ofsuction gas spreads from the pulsation source to the externalrefrigerant circuit via the suction chamber 112 and the combinedpassages 67. The suction chamber 112 and the restricting passages 672reduce the pulsation of suction gas.

In each restricting passage 672, the pressure of refrigerant gasdecreases as the flow rate of refrigerant gas increases. On the otherhand, the pressure of refrigerant gas that has moved from therestricting passage 672 to the corresponding pressure restoring passage671 increases as the flow rate of refrigerant gas decreases in thepressure restoring passage 671. That is, the pressure restoring passage671 restores the pressure of refrigerant gas that has passed through therestricting passage 672. The pressure of refrigerant gas can be reducedin each restricting passage 672 by an amount that can be restored in thecorresponding pressure restoring passage 671. Therefore, thecross-sectional area of each restricting passage 672 can be reduced toincrease the pulsation reducing effect of the suction gas.

If a single combined passage is used at the inlet 28, the differencebetween the diameter of the restricting passage and the diameter of partof the gas passage upstream of the restricting passage becomes great,and the restricting effect of the restricting passage is increased. Inthis case, the length of the pressure restoring passage needs to beincreased. However, when several combined passages 67 are arranged inparallel, the cross-sectional area of each restricting passage 672 canbe reduced. This permits the length of each pressure restoring passage671 to be shortened. Shortening the pressure restoring passages 671shortens the combined passages 67. Shortening the combined passages 67contributes to minimizing the size of the passage forming body 66. Thatis, the structure of arranging several combined passages 67 in parallelis advantageous in suppressing the size of the compressor 10 to whichthe passage forming body 66 is mounted.

The invention may be embodied in the following forms.

The present invention may be applied to compressors other than a scrollcompressor and a piston type variable displacement compressor. Forexample, the present invention may be applied to a swash plate typecompressor or a vane type compressor.

The present invention may be applied to devices that are equipped with amuffler as part of a gas passage in an exhaust system attached to avehicle engine. In this case, the combined passage in which therestricting passage and the pressure restoring passage are connected inseries is provided downstream of the muffler in respect to the gaspassage. The pipe may be deformed by applying pressure on the outercircumferential surface of the pipe. The restricting passage and thepressure restoring passage may be formed in the pipe by suchdeformation.

The present examples and embodiments are to be considered asillustrative and not restrictive and the invention is not to be limitedto the details given herein, but may be modified within the scope andequivalence of the appended claims.

1. A device having a pulsation reducing structure, the devicecomprising: a gas passage; a pulsation source connected to the gaspassage, wherein pulsation of gas spreads from the pulsation source tothe gas passage; a muffler for reducing the pulsation, wherein themuffler is located in a part of the gas passage; and a combined passagelocated in the gas passage, the combined passage is located upstream ordownstream of the muffler with respect to a flowing direction of gas,the combined passage including a restricting passage and a pressurerestoring passage, the restricting passage and the pressure restoringpassage being connected in series, wherein the pressure restoringpassage is located downstream of the restricting passage with respect tothe flowing direction of gas, and wherein the muffler is located betweenthe pulsation source and the combined passage in the gas passage.
 2. Thedevice according to claim 1, wherein the cross-sectional area of thepressure restoring passage is greater than the cross-sectional area ofthe restricting passage.
 3. The device according to claim 1, wherein thecross-sectional area of the pressure restoring passage is graduallyincreased in the flowing direction of gas.
 4. The device according toclaim 1, wherein the pressure restoring passage is widened in theflowing direction of gas.
 5. The device according to claim 4, whereinthe widening angle of the pressure restoring passage is less than orequal to 20 degrees.
 6. The device according to claim 1, wherein thecombined passage is defined by a pipe located in the gas passage.
 7. Thedevice according to claim 6, further comprising a housing that definesthe gas passage, wherein the pipe is formed separately from the housing.8. The device according to claim 6, wherein at least part of the pipe islocated in the muffler.
 9. The device according to claim 8, wherein thepipe also functions as an oil separator, which separates oil from gasflowing through the gas passage.
 10. The device according to claim 6,wherein the pipe includes an introduction passage, the introductionpassage being located upstream of the restricting passage with respectto the flowing direction of gas, wherein the introduction passage isconnected to the restricting passage in series, and the introductionpassage is tapered toward the restricting passage.
 11. The deviceaccording to claim 1, wherein an inlet of the restricting passage iswidened in a direction opposite to the flowing direction of gas.
 12. Thedevice according to claim 1, wherein the combined passage is one of aplurality of combined passages, wherein the combined passages arearranged in parallel.
 13. The device according to claim 1, wherein thedevice is a compressor for a vehicle air conditioner.
 14. The deviceaccording to claim 1, wherein the device is provided in an exhaustsystem attached to a vehicle engine.
 15. A passage forming body having aplurality of combined passages, the combined passages being arranged inparallel, wherein each combined passage includes a restricting passageand a pressure restoring passage, and wherein, in each combined passage,the restricting passage is combined with the pressure restoring passagein series.
 16. A scroll compressor, comprising: a compression mechanismincluding a movable scroll and a fixed scroll, the scrolls defining acompression chamber; a discharge chamber for receiving gas dischargedfrom the compression chamber; a discharge gas passage for guidingdischarge gas from the discharge chamber to the outside of thecompressor; a restricting passage located in the discharge gas passage;and a pressure restoring passage located in the discharge gas passage,wherein the pressure restoring passage is connected to the restrictingpassage in series and located downstream of the restricting passage withrespect to a flowing direction of gas.
 17. The compressor according toclaim 16, wherein the pressure restoring passage is widened in theflowing direction of gas, the widening angle being less than or equal to20 degrees.
 18. The compressor according to claim 16, furthercomprising: a suction chamber for temporarily storing gas before the gasis drawn into the compression chamber; and a suction gas passage forguiding gas into the suction chamber from the outside of the compressor,wherein the suction gas passage includes a suction restricting passageand a suction pressure restoring passage that is located downstream ofthe suction restricting passage with respect to the flowing direction ofgas.
 19. A piston type compressor, comprising: a compression chamber; adischarge chamber into which gas compressed in the compression chamberis discharged; and a discharge gas passage for guiding gas from thedischarge chamber to the outside of the compressor, the discharge gaspassage including a muffler, a restricting passage, and a pressurerestoring passage, wherein the muffler reduces discharge pulsation ofgas, which pulsation spreads from the discharge chamber through thedischarge gas passage, the restricting passage is located downstream ofthe muffler with respect to a flowing direction of gas, and the pressurerestoring passage is located downstream of the restricting passage. 20.The compressor according to claim 19, wherein the pressure restoringpassage is widened in the flowing direction of gas, the widening anglebeing less than or equal to 20 degrees.